RIYADH, Feb 16 (Reuters) - The Saudi Stock Exchange appointed Sarah Al-Suhaimi, chief executive of investment bank NCB Capital, as its first female chair on Thursday, in a sign of change in the conservative society.

Suhaimi was elected by the exchange's board, which includes representatives of the central bank, the finance ministry and the commerce ministry, the exchange said in a statement.

She is the first woman to chair a major government financial institution in the kingdom, where women are forbidden to drive and are subject to a male guardianship system which in many cases restricts their opportunities to work.

Suhaimi, who became the first female chief executive of a Saudi investment bank when she took that post at NCB Capital in 2014, is one of only a few women with a top job in Saudi finance. Her father Jammaz headed the Capital Market Authority between 2004 and 2006.

But her appointment to chair the exchange is in line with an ambitious economic and social reform programme announced by the government last year. One of its goals is to develop women's role in the economy and increase their participation in the workforce to 30 percent from 22 percent in coming years.

Suhaimi will chair the Arab world's largest stock exchange at a critical time. It is preparing to offer its own shares to the public and is trying to win emerging market status from international equity index compilers.

It is also expected next year to list the shares of national oil giant Saudi Aramco in what could be the world's biggest initial public offer.

While heading the exchange, Suhaimi will keep her post at NCB Capital, an arm of National Commercial Bank, Saudi Arabia's largest listed bank, an NCB Capital official said.

(Reporting by Marwa Rashad; Additional reporting by Celine Aswad; Writing by Andrew Torchia; Editing by Susan Fenton) ((andrew.torchia@thomsonreuters.com; +9715 6681 7277; Reuters Messaging: andrew.torchia.thomsonreuters.com@reuters.net))